1 Context
The biggest improvement in timekeeper accuracy was due to the introduction of the oscillator as a time base, first the pendulum by Christiaan Huygens in 1656, then the balance wheel—spiral spring by Huygens and Hooke in about 1675, and the tuning fork by N. Niaudet and L. C. Breguet in 1866, see references [20][5]. Since that time, these have been the only mechanical oscillators used in mechanical clocks and in all watches. (Balance wheels with electromagnetic restoring force approximating a spiral spring are included in the category balance wheel-spiral spring.) In mechanical clocks and watches, these oscillators require an escapement and this mechanism poses numerous problems due to its inherent complexity and its relatively low efficiency which barely reaches 40% at the very best. Escapements have an inherent inefficiency since they are based on intermittent motion in which the whole movement must be stopped and restarted, leading to wasteful acceleration from rest and noise due to impacts. Escapements are well known to be the most complicated and delicate part of the watch, and there has never been a completely satisfying escapement for a wristwatch, as opposed to the detent escapement for the marine chronometer.